1. Field of the Invention
The present invention relates to on-vehicle image pickup apparatuses for displaying an image composed of images taken by a plurality of cameras provided on a vehicle, and in particular to an on-vehicle image pickup apparatus in which the boundary between the vehicle and its surrounding area can be recognized easily.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication Nos. 3-99952, 8-305999, and 3300334 disclose on-vehicle image pickup apparatuses including a plurality of cameras provided on a vehicle. The cameras each include a lens for focusing images in a wide space area, such as a fisheye lens, and detect the images focused by the lenses with a photo-detector, such as a charge-coupled device (CCD).
These on-vehicle image pickup apparatuses compose images of the surroundings of a vehicle taken by the plurality of cameras into a top projection view, and display this composite image in combination with an illustration of the vehicle. This view allows the operator to easily recognize the relationship between the vehicle and it surroundings on a screen.
In capturing the boundary between a vehicle and its surroundings with cameras mounted at two or more locations on the vehicle, the boundary can be displayed almost correctly as a composite image when the cameras are spaced apart from the vehicle, such as on door mirrors. However, cameras mounted at the front end and the rear end of the vehicle are slightly recessed from the front end and the rear end toward the center of the vehicle, respectively. This causes part of the front area and rear area of the vehicle adjacent to the center to be hidden when the front and rear are viewed from the cameras. This makes it impossible to obtain images of the areas close to the front end and rear end of the vehicle even if images taken by the cameras are combined.
Thus, the on-vehicle image pickup apparatus described in Japanese Unexamined Patent Application Publication No. 3300334 processes areas in the surroundings close to the vehicle which cannot be captured as images, for example, to fill the areas with a specific color to indicate dead areas or caution areas.
Such conventional displays, in which the image of the surroundings projected to a plane and the illustration of the vehicle are combined, generally express the outline of the illustration of the vehicle substantially in agreement with the actual outline of the vehicle. This may cause the drivers to make a mistake in measuring the distance between the outline of the illustration of the vehicle displayed on the screen and an obstacle. This may cause the drivers to judge incorrectly that there is enough distance between the illustration of the vehicle and the image of the obstacle on the screen, and thus drive the vehicle abnormally close to the obstacle.
While driving on an inclined road or an extremely rough road, vehicles may bounce to cause the outer ends of the vehicle to roll to the right and left greatly. This may cause the vehicle to collide with obstacles on either side of the road. However, the driver can hardly avoid approaching the obstacles due to the rolling of the vehicle when driving while viewing the illustration of the vehicle displayed on the screen.
If the dead area or caution area is filled with a specific color as in Japanese Unexamined Patent Application Publication No. 3300334, the operator who views the display screen cannot intuitively understand what the filled portion indicates, that is, whether the filled portion indicates part of the vehicle or the ground or the like. This makes it difficult for the operator to grasp the position of the outer periphery of the vehicle.